1. Field of the Invention
The present invention relates to an electroplating bath containing citric acid or citrate used for tin or tin alloy plating.
2. Description of the Background Art
Electroplating baths containing citric acid or citrate for tin or tin alloy plating are disclosed in Japanese Patent Publication Nos. 59-48874 and 59-48875.
In the former Japanese patent publication, water soluble polymer obtain polymerization of epoxy compound, and ethylene glycol, propylene glycol or glycerol is added to a tin or tin alloy plating bath of pH 4-8 containing citric acid or citrate and ammonium salt. In the latter Japanese patent publication, water soluble polymer of polyoxyethylene or derivative thereof is added to a tin or tin alloy plating bath of pH 4-8 containing citric acid or citrate and ammonium salt. Bright deposited films can be obtained by either plating bath.